Newton, Utah, dairy producer Cassie McKinnon hasn’t seen an outbreak of highly pathogenic avian influenza in her herd. But some of her neighbors have.
She’s seen their animals appearing lethargic and slow, and generally not looking very healthy. And her family is placing an extra emphasis on biosecurity.
“We try to do as much prevention as we can,” McKinnon said. “We make sure the guys are using protective equipment. We try to do what we do until they tell us something different.”
McKinnon had just attended a seminar at World Ag Expo on the unexpected battle against avian flu in U.S. dairy, presented by scientists from University of California, Davis. An exploratory economic analysis estimated the outbreak that has ravaged herds in the San Joaquin Valley and elsewhere has cost the industry about $198 per quarantined cow daily, emphasizing the economic strain and the critical need for containment.
But while the session went into detail about biosecurity protocols and the need for the industry, government agencies and universities to work together to find solutions, clinical researcher Richard Pereira noted that scientists are still trying to understand things like how the disease spreads within herds, how long immunity lasts and what the chances are for reinfection.
“We know the high-risk areas tend to be the parlor and milkers,” Pereira said. “But we don’t know how aerosolized (the virus) is.”
Likewise, Luis Garcia-Covarrubias, an agricultural and environmental economist, said researchers don’t know why California suddenly became the epicenter of dairy outbreaks last fall, although the concentration of cows in the Golden State may have something to do with it.
“There’s no coincidence in the number of cows (infected) in each state,” he said.
McKinnon acknowledged she was “a little disappointed” by the lack of information. “Right now they’re in the analysis stage,” she said.
Still spreading
The research comes as the virus that has been devastating farm animals since 2022 shows few signs of abating. The flu is widespread in wild birds worldwide and is causing outbreaks in poultry and U.S. dairy cows, with 69 human cases reported as of Feb. 19, according to the U.S. Centers for Disease Control and Prevention.
Nationwide, HPAI has affected 162.5 million poultry and 972 dairy herds, the CDC reports. Among infected dairy herds, 747 were in California, with 297 of those fully recovered and released from quarantine, notes the California Department of Food and Agriculture. In the West, HPAI had also infected dairies in Colorado (64 cases), Idaho (35 cases), Utah (13 cases), Nevada (seven cases), Wyoming (one case) and Arizona (one case) as of Feb. 19, according to the USDA.
Arizona’s case was discovered Feb. 11, and the dairy in Maricopa County has been placed under quarantine. In Nevada, state and federal agriculture officials have stepped up preventive measures after dairies in Nye and Churchill counties recently showed detections of HPAI. The USDA is continuing testing to confirm what strain it is in Churchill County, but preliminary results show it is consistent with a strain that has also been seen in wild birds in North American flyways, the state Department of Agriculture reports.
“The challenge with this virus is that it may be spread through contaminated clothing worn and equipment shared between animals, but birds carrying the disease can also infect domestic animals and livestock,” said agency director J.J. Goicoechea, a veterinarian. To help prevent the spread, the NDA and USDA announced it would begin removing a “nuisance population” of non-native European starling populations in several counties.
Nationwide, the USDA’s Animal and Plant Health Inspection Service has been working with state veterinarians to collect raw milk samples to better assess where the H5N1 virus is present, with a goal to better inform biosecurity and containment measures. The USDA used bulk milk testing to eradicate brucellosis from dairy herds.
APHIS has also approved field trials for several possible vaccines for H5N1 in cattle and other species. The USDA recently granted conditional approval for a new bird flu vaccine for poultry developed by New Jersey-based Zoetis.
What scientists do know
The H5N1 virus isn’t new, UC Davis’ Garcia-Covarrubias explained. It was first identified in 1996 in China and spread throughout Asia, Africa and Europe in the early 2000s, according to the CDC. New strains started emerging in 2014-16 and spread widely, and the strain that is affecting U.S. agriculture was first detected overseas in 2021, the CDC reports.
While the virus is usually fatal in birds, most cattle recover after a couple of weeks, but their illness comes at a great cost to producers. The losses add up quickly; a 2,500-cow dairy under quarantine could lose close to $500,000 a day in added treatment and labor costs and lost production, Garcia-Covarrubias said.
In California, it takes an average of 81 days for a dairy to get off quarantine after three successive negative bulk milk tests, state veterinarian Annette Jones said in a recent webinar. About 300 dairies were in the process of testing out as of Feb. 18, she said. When at least 70% of cows in a population develop immunity, the virus tends to disappear, she said.
Jones said three things will sustain agriculture:
Biosecurity. Continue to support enhanced practices on dairies and poultry farms to reduce the amount of virus moved and to protect susceptible animals.
Testing. Continue mandatory testing for influenza in dairy cattle and poultry to understand how the virus is changing and how to adjust disease control strategies and educate owners and buyers.
Reduce viral load. Reduce virus in the environment through population immunity or euthanasia and farm disinfection so that biosecurity measures aren’t overwhelmed.
“All of these three things have to happen, and I would suspect it will happen in perpetuity,” she said. “We will probably have to use this three-legged stool approach for the foreseeable future.”